Opposed-angle brush holder



1945. a. P. LESSMANN 3 OPPOSED-ANGLE BRUSHHOLDER Filed NOV. 6,,1943

WITNESSES:

INVENTOR g 4' Gerhard/716 5509900.

ATTORNEY Patented Aug. 21, 1945 UNITED ,s'rnrss PATENT 1 OFFICE 2Claims. (Cl. 171- 324) My invention relates to brushhoiders forholdlDIlt'WO brushesin operative relation to a rotating commutator, atopp sed angles with respect to theradial direction, so that thebrushholdersacan be used, without change or adiustment, 'ondynamin-electric machines having both directions of rotation.

*Bmshholders having two (or more) :brushes *(two in the circumferentialdirection), have a guest ::advantage over single-brush brushholders, inthat any roughness or elevation in the commutator surface will notstrike two circumferentially displaced brushes simultaneously, and hencethe entire -:current will be carried, inomentarllmiby one brush whilethe other ibrush jumps off of the commutator-surface due to roughness.

Heretofore, two-brush brushholders have been of two "types, and bothhave suffered disadvantages. In one .type, the two brushes have beenparallel to each other, the brushholder had to be taken off andremounted to accommodate a reversed direction of rotation, two'springsrwere required for the two brush-fingers, the springpressure wasnot well compensated against changes due to the :a'mount of brush-wear,and the number of parts, andihence the cost, were excessive. In theother type, the two brushes were at opposed 'angleaso that themaohineoould rotate in either direction, a single spring was sometimesused for the two hrush-fingers, and the number of parts was reduced, butthe spring was not compensated against the efiects of brushwear, so thatthe pressure on the brush decreased excessively as the length of thebrush became smaller because of wear, and there were also otherdisadvantages, such as excessive lateral pressure on the brushes.

It is an object of my present invention to provide an improved V-type oropposed-angle up, only one spring is used, to provide pressuredouble-brush brushholder utilizing a linearly acting spring which isconnected to the brushfinger, or to both-brush-fingers', at such aposition and angle that the change in the leverage or moment-alarm ofthe spring automatically compensates the finger-pressure for practicallyconstant brush-pressure against the commutator, within very narrowlimits, during the entire life of the brush. No spring-adjustment isrequired, therefore, during the life of the brush, to make up for wearor to compensate for the reduced spring-pressure or for altered angle ofapplication of the brush-finger pressure, as the brushfinger follows upthe brush as the brush wears away.

Other objects of my invention are to provide-a new double-brushbrushholder which can be manufactured at less cost than eitherof thelpl'esent or previously known'common types of doubilebrush brushholders,and which has numerous other important advantages, among which may bementioned: I

(a/l A design suitable tor either-casting or inbricatiOn romsheet-metal.

-(b) Only one shape of finger is required, not a separate finger forrightand left-"hand mounting.

(c) The compensating leverage previously mentioned.

(d) The arrangement permits the removal and exchange of either brushwithout disturbing the other brush. a i

(a) One old brush and :one new brush may he used, without choice ofposition.

(f) In replacing a. worn or defective brush, the brush-finger pullsover-center when lifted off of the brush, and thus locks itself in itselevated position, freeing one hand for the exchange 'of brushes.

(9) The new brushholder fits old brush-rigging interchangeably with olholders.

:(h) The center part of the new holder can :be made the same for allsizes of brushes, thus reducing the number of patterns or tools.

(i) It has a reduced number of parts.

' (1') For (brush-to-radius) angles of 25 and for both brush-fingers.

Three exemplary forms of embodiment of:my new brushholder are shown inthe drawing, wherein Fig. 1 is a 'top'plan viewof a two-gang V-typebrushholder utilizing only one spring .for the two "opposed-anglebrushes, one of the gangs or brushholders being shownempty; Fig. 2-is aside-elevationa-l view of the brushholder shown in Fig. 1.; Fig. 3 is aside-elevational view of a V-ty-pe brushholder "having an angle oflessthan 25" and consequently utilizing two springs for the twobrush-fingers; and Fig. 4 is .a view similar to Fig. -3, illustratingthe equivalence of a compression spring in place of a tension spring.

In the form shown in Figs. 1 and 2, two brushholders l and 2 are placedside-by-side, with only one mounting-pad 6, in what is known as atwogang brushholder. To facilitate the illustration, one brushholder, l,is shown bare, in Fig. 1, without any loose or movable parts. Eachbrushholder proper comprises a V-shaped center part I, having anangularly disposed or inclined brushbox 8 on each side, and havingupstanding fingersupporting arms l which are notched at l2 to receivethe pivot-pins 14.

Associated with each brushholder proper, are two identical brush-fingersl6, of which only one will be described, and the reference-numerals willbe applied only to it, so that its outline may be more readily traced.It has a U-shaped mounting-portion carrying the laterally extendingpivot-pins I4. From one side or leg of the U, there extends a downwardlycurving finger-arm Hi, the tip IQ of which is bent, for engagement withthe top of the brush 2|. Each finger |6 has its pivot-pins l4 seated inthe notches |2 in one side of the brush-holder, and it has itsfinger-arm |8 extending over to the far brush 2|, so as to obtain aslong a finger-arm as possible.

It is an important feature of my invention that I utilize a linearlyacting spring 23, which is so connected to the brush-fingers l6 that itsleverage changes, as the finger swings in following up the brush as itwears on the commutator 24, thus automatically compensating forbrush-wear} as previously mentioned.

In the form of my invention shown in Figs. 1 and 2, only one spring 23is used for the two brush-fingers l6, and the spring is a tensionspring.Each finger l6 has an upstanding rearportion 25 of the U-shapedmounting-portion l1, and said upstanding rear-portion 25 is providedwith two notches 26 and 21, either one of which may be utilized to seata cross-pin 28 which carries one end of the spring 25, in one notch orthe other according to the spring-tension desired.

It will be noted that the center-line of the spring 23 lies above thepivot-point H of each finger l6, thus providing a moment-arm for thelinearly applied spring-force, tending to rotate the finger-arm I8downwardly. It will further be noted that the lever-arm, from M to' 26,extends backwardly, as well as upwardly, so that, as the finger-arm |8swings downwardly, following the top of the brush 2| as the brush wearson the commutator 24, the rear end 26 of the spring 23 swings upwardly,increasing the spring-moment or vertical distance between thecenter-line of the spring and the finger-pivot l4. This is the automaticpressure-compensating feature of which I have spoken. Without it, thebrush-pressure would fall off quite considerably as a result ofbrush-wear.

When the finger |8-| 9 is lifted ofi of the brush 2|, as for the purposeof replacing the brush, the rearwardly inclined spring-lever-arm 26-14again makes itself felt, because the springterminal 26 swings downwardlyuntil the center'- line of the spring falls slightly below the finger-'pivot l4, thus locking the finger in its elevated position, as shown indotted lines at I9, so that the operator will not need to use one handto hold up the finger while he replaces the brush. At the same time thespring is only slightly extended, so that the spring-tension on theother finger is only slightly increased while the first finger is in itslocked elevated position l9, thus not interfering with the operation ofthe other brush, while the defective brush is being replaced.

In common with modern practice, reaction-type brushes 2| are utilized,having inclined or wedgeshaped top-pieces 29 so that the pressure of thefinger-tip l9 will have a component or reaction tending to hold one sideof the brush against one side of the box 8, thus avoiding rattling orchattering of the brush.

By utilizing a construction in which the fingerarm IB is long, I reducethe length of arc through which the finger must swing during the usefullife of the brush, and I avoid obtaining excessive lateral pressures onthe brush at either extreme position of th finger.

Other advantageous features of the operation of my brushholder will beobvious from the construction shown in Figs. 1 and 2, and from thestatement of the nature and objects of my invention.

In Figs. 3 and 4, I illustrate a manner in which my invention may beapplied to V-type brushholders in which the brush-to-radius angle is toosmall to readily provide room for'the overlying brush-fingers andsingle-spring construction of Figs. 1 and 2. In Figs. 3 and 4, thefingers l6 are mounted on laterally extending arms 3| on the brush-boxes8', the finger-pivot being indicated at M. Because of this arrangement,a separate spring 32 is provided for each brush-finger i 6. As in thesingle-spring design of Figs. 1 and 2, the spring may be either atension spring 32, as shown in Fig. 3, or a compression-spring 32, asshown in Fig. 4. In either case, the line of action and thespring-lever-arm are so chosen as to have the pressure-compensatingadvantages, and the over-center, locked, elevated finger positionfeature already described. i

While I have illustrated my invention in three preferred forms ofembodiment, these forms are nevertheless only illustrative, as manychanges may be made without departing from some of the broader featuresand advantages of my invention. I desire, therefore, that the appendedclaims shall be accorded the broadest construction consistent with theirlanguage.

I claim as my invention:

1. An opposed-angle double-brush brushholder comprising a V-shapedcenter part, an inclined brush-box on each side thereof, two upstandingfinger-supporting arms, one on each side of the brushholder, twofingers, each finger being pivot ed on the finger-supporting arm on oneside of the brushholder and extending over to the brushbox on the otherside of the brushholdeneach finger having an extended, downwardly curvedfinger-arm having a finger-tip adapted to engage the top of a brush, anda linearly acting spring having its respective ends in engagement withthe respective fingers for biasing the fingers toward the respectivebrushes.

2. The invention as defined in claim 1, characterized by said twofingers being identical and GERHARD P. LESSMANN.

